Adsorbent for aromatic hydroxy compound and utilization thereof

ABSTRACT

An adsorbent to an aromatic hydroxy compound, which comprises composite metal oxide solid solution particles of the following formula (1) or hydrotalcite-like composite metal hydroxide particles of the following formula (2), and a method of removing an aromatic hydroxy compound in a solvent by using the adsorbent.  
     (Mg y1 M 2+   y2 ) 1−x Al x O 1+0.5x   (1)  
     (Mg y1 M 2+   y2 ) 1−z Al z (OH) 2+a (A n− ) b   .m H 2 O  (2)  
     Provided according to the present invention is an adsorbent capable of efficiently removing an aromatic hydroxy compound from an aqueous solvent or an organic solvent containing an aromatic hydroxy compound.

DETAILED DESCRIPTION OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The present invention relates to an adsorbent to an aromatichydroxy compound and a method of removing an aromatic hydroxy compoundfrom a liquid medium containing an aromatic hydroxy compound byadsorption.

[0003] 2. Prior Art of the Invention

[0004] Metal oxide particles and metal hydroxide particles such asmagnesium oxide particles, aluminum hydroxide particles and hydrotalcitecompound particles are nowadays used as an adsorbent to a variety ofacids and alkalis. However, these metal oxide particles or metalhydroxide particles exhibit no capability of adsorption to an aromatichydroxy compound or an amine compound, or their adsorptive capability ispoor.

[0005] Of aromatic hydroxy compounds, a bisphenol compound typified bybisphenol A is not only used as a raw material for polymers such as apolycarbonate resin and an epoxy resin, but also used for a plasticpolyester, an antioxidant and a vinyl chloride resin stability, and itis assumed that a worldwide output thereof exceeds approximately 1.70million tons.

[0006] In recent years, however, it has been clearly shown that anaromatic hydroxy compound such as bisphenol A eluted from the aboveresins works as an endocrine disrupter to cause greatly detrimentaleffects on the human body and an ecosystem. Under the circumstances,investigations of rivers and underground waters have proceeded, and agovernment agency has reported that rivers and ground waters in manyareas are contaminated with aromatic hydroxy compounds. There is anotherreport that an aromatic hydroxy compound has been detected in tap water.

[0007] However, no report has been found at present concerning a method,an adsorbent, etc., for effectively removing the above eluted aromatichydroxy compounds from an organic solvent.

[0008] Problems to be Solved by the Invention

[0009] It is an object of the present invention to provide an adsorbentcapable of effectively removing an aromatic hydroxy compound from awater or an organic solvent containing an aromatic hydroxy compound anda use thereof.

[0010] Means to Solve the Problem

[0011] According to the present invention, there is provided adsorbentsto an aromatic hydroxy compound, the adsorbent comprising compositemetal oxide solid solution particles of the following formula (1) orhydrotalcite-like composite metal hydroxide particles of the followingformula (2).

(Mg_(y1)M²⁺ _(y2))_(1−x)Al_(x)O_(1+0.5x)  (1)

(Mg_(y1)M²⁺ _(y2))_(1−z)Al_(z)(OH)_(2+a)(A^(n−))_(b) .mH₂O  (2)

[0012] wherein M²⁺ is divalent metal ion or ions of Zn²⁺ and/or Ca²⁺,A^(n−) is an anion having a valence of n, and y₁, y₂, x, z, a, b and msatisfy the following conditions.

y ₁ +y ₂=1

0<y ₁≦1

0.1<x<0.5

0.1<z<0.5

z=a+nb

a>0.1z

0≦b<z/n

0≦m<2

[0013] According to the present invention, further, there is provided amethod of removing an aromatic hydroxy compound in an aqueous solvent ororganic solvent containing an aromatic hydroxy compound, which comprisesbringing the above solvent and the adsorbent of the present inventioninto contact with each other to allow the adsorbent to adsorb thearomatic hydroxy compound.

[0014] The present invention will be explained in detail hereinafter.

[0015] While the mechanism of adsorption of the above adsorbent to anaromatic hydroxy compound is not clear, the present inventors'assumption is that the adsorption is ion exchanging depend on adifference between the dissociation constant of an aromatic hydroxycompound and the counterpart of the adsorbent as will be explainedbelow.

[0016] For developing a selective adsorbent to an aromatic hydroxycompound, first, the present inventors paid attention to a height ofdissociation constant (pKa) of an aromatic hydroxy compound. A typicallyknown hydrotalcite compound of the following formula (3) generallycontains, as an anion (A^(n−)), a fixed amount or more of at least oneanion selected from the group consisting of CO₃ ²⁻, SO₄ ²⁻, Cl⁻, NO₃ ⁻and CH₃COO⁻. The typical hydrotalcite compound of the formula (3) is aconsiderably strong acid due to a conjugated acid based on the anion ascompared with an aromatic hydroxy compound. It is therefore assumed thatthere is a difficulty in an aromatic hydroxy compound undergoingdissociation to ion-exchange with an anion (A^(n−)) of the hydrotalcitecompound (In fact, this assumption is also considered correct on thebasis of Comparative Examples 1 and 2 to be described later).

(M²⁺)_(1−x)Al_(x)(OH)₂(A^(n−))_(x/n) .mH₂O  (3)

[0017] wherein M²⁺ is divalent metal ion or ions of Mg²⁺ and/or Zn²⁺,An⁻ is an anion having a valence of n and at least one member selectedfrom the group consisting of CO₃ ²⁻, SO₄ ²⁻, Cl⁻, NO₃ ⁻ and CH₃COO⁻, xsatisfies 0.1<x<0.5, and m is a positive number.

[0018] Further, it is also presumably because carbon dioxide gas isadsorbed on the crystal surface of each particle of the hydrotalcitecompound of the above formula (3) that the typical hydrotalcite compoundparticles cannot adsorb an aromatic hydroxy compound.

[0019] For removing the anion as many as possible that inhibits theadsorption to an aromatic hydroxy compound, therefore, the presentinventors have paid attention to composite metal oxide solid solutionparticles of the following formula (1), which are obtained by calciningthe hydrotalcite compound particles of the formula (3).

(Mg_(y1)M²⁺ _(y2))_(1−x)Al_(x)O_(1−0.5x)  (1)

[0020] wherein M²⁺ is divalent metal ion or ions of Zn²⁺ and/or Ca²⁺,and y₁, y₂ and x satisfy the following conditions.

y ₁ +y ₂=1

0<y ₁≦1 (preferably 0.5<y ₁≦1)

0.1<x<0.5 (preferably 0.2≦x≦0.4)

[0021] When the composite metal oxide solid solution particles of theabove formula (1) were brought into contact with an aqueous or organicsolvent containing an aromatic hydroxy compound, it was found that thearomatic hydroxy compound is efficiently adsorbed to the above solidsolution particles.

[0022] The present inventors have also found that particles of ahydrotalcite-like composite metal hydroxide of the following formula(2), obtained by hydrating the composite metal oxide solid solutionparticles of the above formula (1), have excellent capability ofadsorption to an aromatic hydroxy compound as well.

(Mg_(y1)M²⁺ _(y2))_(1−z)Al_(z)(OH)_(2+a)(A^(n−))_(b) .mH₂O  (2)

[0023] wherein M²⁺, y₁ and y₂ are as defined in the above formula (1),A^(n−) is an anion having a valence of n, preferably at least one anionselected from the group consisting of CO₃ ²⁻, SO₄ ²⁻, Cl^(−, NO) ₃ ⁻ andCH₃COO⁻, and z, a, b and m satisfy the following conditions.

0.1<z<0.5 (preferably 0.2≦z≦0.4)

z=a+nb

a>0.1z (preferably a>0.5z)

0≦b≦z/n (preferably 0≦b<0.5z/n)

0≦m<2 (preferably 0≦m≦1)

[0024] The hydrotalcite-like composite metal hydroxide particles of theabove formula (2) are a compound of which the anion (A^(n−)) content isdecreased to a considerable extent in view of its chemical formula ascompared with the hydrotalcite compound of the above formula (3).

[0025] Advantageously, the adsorbent comprising particles of thecompound of the above formula (1) or (2), provided by the presentinvention, has a BET specific surface area in the range of from 10 to250 m²/g, preferably from 20 to 220 m²/g. When the specific surface areais large, the filtering rate of the adsorbent after adsorption tends todecrease. However, a decrease in the filtering rate can be overcome whenthe adsorbent is formed by granulation of a powder.

[0026] The composite metal oxide solid solution particles of the formula(1) in the present invention can be produced, for example, by calciningthe hydrotalcite compound of the above formula (3), particularly, ahydrotalcite compound whose anion (A^(n−)) is carbonate anion (CO₃ ²⁻)at a temperature of 400 to 900° C. When the calcining is carried out ata temperature higher than the above upper limit, the adsorptivecapability of obtained composite metal oxide solid solution particles islow, and further, when the hydrotalcite-like composite metal hydroxideparticles of the formula (2) are produced by hydrating a solid solutionthereof, a reaction therefor sometimes does not proceed smoothly.

[0027] The hydrotalcite-like composite metal hydroxide particles of theformula (2) can be produced by calcining the hydrotalcite compoundparticles of the formula (3) at 400 to 900° C. as described above toobtain the composite metal oxide solid solution particles of the formula(1) and then hydrating the obtained particles in water. Further, theabove particles can be also synthesized according to a method describedin JP-B-51-6040. In the production of the hydrotalcite-like compositemetal hydroxide particles of the formula (2), preferably, the content ofcarbonic acid or carbon dioxide gas in the reaction system therefor isdecreased so that the content thereof is as less as possible. The reasonis that carbonate ion as an anion is included in the structure of thehydrotalcite-like composite metal hydroxide particles or that CO₂ isadsorbed on a crystal surface so that the adsorptive capability isdegraded.

[0028] Since, however, the hydrotalcite-like composite metal hydroxideparticles have high capability of adsorption to phenols, other aniondoes not cause any special problem so long as the hydrotalcite-likecomposite metal hydroxide particles themselves are contained.

[0029] After calcining, preferably, the metal composite oxide solidsolution particles that constitute the adsorbent of the presentinvention are similarly stored such that surface adsorption to carbondioxide gas does not proceed.

[0030] Particles of the adsorbent of the present invention can be usedin various forms for adsorption. That is, when these adsorbent particlesare prepared by the above calcining or hydration, generally, they areobtained in the form of a fine powder or a spherical powder having anaverage particle diameter of 30 to 200 μm. These powders can be used asan adsorbent as they are. Further, they can be used as an adsorbenthaving the form of granules or pellets having an average diameter of 0.7to 3 mm by granulating the above particles. Further, the adsorbent canbe used in the thus-obtained form, or a solvent containing an aromatichydroxy compound may be flowed through a column charged with theadsorbent.

[0031] The adsorbent of the present invention comprises the abovecomposite metal oxide solid solution particles or the abovehydrotalcite-like composite metal hydroxide particles, and it may beformed of these particles per se or may be formed by granulating theparticles with a binder. The adsorbent contains at least 50% by weight,preferably at least 70% by weight, particularly preferably at least 80%by weight of the above particles.

[0032] According to the present inventors' finding, thehydrotalcite-like composite metal hydroxide particles of the formula (2)are more preferred than the composite metal oxide solid solutionparticles of the formula (1) for removing an aromatic hydroxy compoundfrom an organic solvent containing an aromatic hydroxy compound byadsorption. In the composite metal oxide solid solution particles of theformula (1), the concentration of an aromatic hydroxy compound containedin an organic solvent can be decreased to approximately 10 ppm byincreasing the amount thereof. However, it is difficult to remove thearomatic hydroxy compound by adsorption when the concentration thereofcomes to be smaller or several ppm. In contrast, the hydrotalcite-likecomposite metal hydroxide particles of the formula (2) can nearlycompletely remove an aromatic hydroxy compound in an organic solvent byadsorption by using them in a small amount as compared with thecomposite metal oxide solid solution particles of the formula (1).

[0033] However, when the solvent containing an aromatic hydroxy compoundis an aqueous solvent, part of the composite metal oxide solid solutionparticles are hydrated during a contact adsorption reaction to beconverted to hydrotalcite-like composite metal hydroxide particles, sothat an aromatic hydroxy compound can be completely removed byadsorption even in case that the composite metal oxide solid solutionparticles are used.

[0034] According to the present invention, therefore, the method ofremoving an aromatic hydroxy compound in a solvent by adsorptionincludes the following methods (a) and (b) as preferred embodiments.

[0035] (a) A method of removing an aromatic hydroxy compound in anaqueous solvent containing an aromatic hydroxy compound, which comprisesbringing the aqueous solvent and the adsorbent of the formula (1) or (2)into contact with each other to allow the adsorbent to adsorb thearomatic hydroxy compound.

[0036] (b) A method of removing an aromatic hydroxy compound in anorganic solvent containing an aromatic hydroxy compound, which comprisesbringing the organic solvent and the adsorbent comprising thehydrotalcite-like composite metal hydroxide of the formula (2) intocontact with each other to allow the adsorbent to adsorb the aromatichydroxy compound.

[0037] The aromatic hydroxy compound as an object of adsorption in thepresent invention is preferably a monohydroxy compound or a dihydroxycompound, and it specifically includes compounds that are used as a rawmaterial or a terminal-blocking agent for the synthesis of apolycarbonate resin, an epoxy resin or a polyester resin. Examplesthereof include phenol or bisphenol. These compounds may havesubstituents such as an alkyl group, a halogen and a nitro group. Thebisphenol includes a compound represented by HO—PH—Z—PH—OH (in which PHis a 1,4-phenylene group, and Z is a direct bond, an oxygen atom, asulfur atom, a sulfoxide group, a sulfone group, an alkylidene grouphaving 30 or less carbon atoms, an alkylene group having 30 or lesscarbon atoms, a cycloalkylidene group having 30 or less carbon atoms, acycloalkylene group having 30 or less carbon atoms, or aphenyl-sbustituted alkylene group having 30 or less carbon atoms). Atypical example of the bisphenol is 2,2-bis(4-hydroxyphenyl)propane(bisphenol A).

[0038] In the present invention, examples of the “organic solvent” forthe organic solvent containing an aromatic hydroxy compound include (i)lower alcohols such as methanol, ethanol, propanol and butanol, (ii)ethers such as diethyl ether, diisopropyl ether, tetrahydrofuran anddioxolane, (iii) ketones such as acetone, methyl ethyl ketone, methylisobutyl ketone and acetophenone, (iv) aliphatic hydrocarbons such ashexane, heptane and octane, (v) aromatic hydrocarbons such as benzene,chlorobenzene, toluene and xylene, (vi) esters such as ethyl acetate,propyl acetate and higher fatty acid esters (e.g., glyceride), (vii)nitrogen-containing compounds such as pyridine, N-methylpyrrolidone anddimethylacetamide, and (viii) nitriles such as acetonitrile andpropionitrile. The above organic solvents may be used alone or as amixture in combination of at least two of them. The content of theorganic solvent in the entire solvent is at least 60% by weight,preferably at least 80% by weight, particularly preferably at least 90%by weight, and the organic solvent may contain a small amount of water.The aqueous solvent is a solvent whose water content based on the entiresolvent is at least 60% by weight, preferably at least 80% by weight,particularly preferably at least 90% by weight, and the aqueous solventmay contain a small amount of an organic solvent.

[0039] As a method of removing an aromatic hydroxy compound in a solventby adsorption by means of the adsorbent of the present invention, therecan be used an adsorption method that is generally known per se. Forexample, there is a method in which the adsorbent is added to a solvent,the mixture is stirred and then the adsorbent is separated with afilter. There may be also employed a method in which the adsorbent ischarged into a column and a solvent is flowed through the column. Whenthe column is used, it is preferred to employ a means of preventing adecrease in the adsorption rate caused by adsorption to carbon dioxidegas. That is, for example, there can be employed a method in whichparticles of the adsorbent are suspended in an organic solvent andimmediately charged into the column or a method in which the adsorbentin the form of granules (or pellets) is charged into the column andimmediately thereafter an organic solvent is flowed through. There canbe also employed a method in which the adsorbent is suspended in adecarboxylated aqueous solvent and immediately charged into the columnor a method in which the adsorbent in the form of granules (or pellets)is charged in the column and immediately thereafter a decarboxylatedaqueous solvent is flowed through.

[0040] In the adsorption procedure, while the temperature particularlyis not limited, the adsorption can be carried out generally at atemperature of 0 to 150° C., preferably 20 to 100° C. Generally, as thetemperature increases, the processing time decreases.

[0041] After the adsorption procedure, the adsorbent that has adsorbedan aromatic hydroxy compound is calcined, for example, at a temperatureof 400 to 900° C. and the calcined adsorbent is hydrated as required,whereby the thus-treated adsorbent can be used again as an adsorbent ofthe present invention.

[0042] According to the present invention that has been discussedhereinabove, the separation and recovery of an aromatic hydroxy compoundin a solution resulting from the step of producing a synthetic resinfrom an aromatic hydroxy compound as a raw material can be selectivelyand effectively carried out.

[0043] Having paid attention to excellence of the composite metal oxideparticles of the above formula (1) and the hydrotalcite-like compositemetal hydroxide particles of the above formula (2) in the property ofadsorbing an aromatic hydroxy compound, the present inventors havestudied other use. As a result, it has been found that when theadsorbent of the present invention is incorporated into a syntheticresin or paint synthesized from an aromatic hydroxy compound as a rawmaterial, an aromatic hydroxy compound that remains as an unreacted rawmaterial or is generated by decomposition can be effectively adsorbed.That is, it has been found that when the adsorbent of the presentinvention is incorporated into a synthetic resin or paint containing anaromatic monohydroxy compound, the elution or volatilization of aharmful aromatic hydroxy compound from the synthetic resin or paint isinhibited.

[0044] According to the present invention, there is provided a resincomposition or coating composition containing a synthetic resin or paintsynthesized from an aromatic hydroxy compound as a raw material and theadsorbent of the present invention.

[0045] As an adsorbent to be incorporated into the synthetic resin orthe paint, an adsorbent comprising the hydrotalcite-like composite metalhydroxide particles of the formula (2) is more preferred than anadsorbent comprising the composite metal oxide particles of the formula(1) in respect of adsorption properties and stability to the resin (orpaint). As the above synthetic resin, preferred is a polycarbonate resinor an epoxy resin synthesized from bisphenol A as a raw material. Theamount of the adsorbent per 100 parts by weight of the synthetic, resinor paint is 0.01 to 10 parts by weight, preferably 0.05 to 5 parts byweight.

EXAMPLES

[0046] The present invention will be specifically explained withreference to Examples hereinafter.

Example 1

[0047] Carbonate-anion-possessing hydrotalcite particles having a BETspecific surface area of 100 m²/g and represented by a chemical formulaof Mg_(0.7)Al_(0.3)(OH)₂(CO₃)_(0.15).0.55H₂O were calcined at 550° C.for 2 hours, to give composite metal oxide solid solution particlesMg_(0.7)Al_(0.3)O_(1.15) having a BET specific surface area of 202 m²/g.

Example 2

[0048] The composite metal oxide solid solution particles obtained inExample 1 and decarboxylated water having a weight approximately 10times the weight thereof were placed in a container, and the containerwas closed and shaken in a constant-temperature chamber at 30° C.overnight, to carry out a rehydrative reaction. The resultant mixturewas dehydrated and dried to give hydrotalcite-like composite metalhydroxide particles Mg_(0.7)Al_(0.3)(OH)_(2.2)(CO₃)_(0.05).0.65H₂Ohaving a BET specific surface area of 32 m²/g. The carbonate ion of theabove formula is that which was derived from inclusion of CO₂ in air inthe process of the dehydration and drying.

Example 3

[0049] Carbonate-anion-possessing hydrotalcite particles having a BETspecific surface area of 14.5 m²/g and represented by a chemical formulaof Mg_(0.75)Al_(0.25)(OH)₂(CO₃)_(0.125).0.5H₂O were calcined at 550° C.for 2 hours, to give composite metal oxide solid solution particlesMg_(0.75)Al_(0.025)O_(1.125) having a BET specific surface area of 143m²/g.

Example 4

[0050] The composite metal oxide solid solution particles obtained inExample 3 and decarboxylated water having a weight approximately 10times the weight thereof were placed in a container, and the containerwas closed and shaken in a constant-temperature chamber at 30° C.overnight, to carry out a rehydrative reaction. The resultant mixturewas dehydrated and dried to give hydrotalcite-like composite metalhydroxide particles Mg_(0.75)Al_(0.25)(OH)_(2.17)(CO₃)_(0.042).0.7H₂Ohaving a BET specific surface area of 31 m²/g. The carbonate ion of theabove formula is that which was derived from inclusion of CO₂ in air inthe process of the dehydration and drying.

Example 5

[0051] Zinc-containing and carbonate-anion-possessing hydrotalciteparticles having a BET specific surface area of 9.0 m²/g and representedby a chemical formula ofMg_(0.5)Zn_(0.17)Al_(0.33)(OH)₂(CO₃)_(0.165).0.5H₂O were calcined at550° C. for 2 hours, to give composite metal oxide solid solutionparticles Mg_(0.5)Zn_(0.17)Al_(0.33)O_(1.165) having a BET specificsurface area of 140 m²/g.

Example 6

[0052] The composite metal oxide solid solution particles obtained inExample 5 and decarboxylated water having a weight approximately 10times the weight thereof were placed in a container, and the containerwas closed and shaken in a constant-temperature chamber at 30° C.overnight, to carry out a rehydrative reaction. The resultant mixturewas dehydrated and dried to give Zinc-containing hydrotalcite-likecomposite metal hydroxide particlesMg_(0.5)Zn_(0.17)Al_(0.33)(OH)_(2.22)(CO₃)_(0.06).0.6H₂O having a BETspecific surface area of 60 m²/g. The carbonate ion of the above formulais that which was derived from inclusion of CO₂ in air in the process ofthe dehydration and drying.

Comparative Example 1

[0053] Carbonate-anion-possessing hydrotalcite having a BET specificsurface area of 100 m²/g and represented by a chemical formula ofMg_(0.7)Al_(0.3)(OH)₂(CO₃)_(0.15).0.55H₂O used as a raw material inExample 1.

Comparative Example 2

[0054] Zinc-containing and carbonate-anion-possessing hydrotalciteparticles having a BET specific surface area of 9.0 m²/g and representedby a chemical formula ofMg_(0.5)Zn_(0.17)Al_(0.33)(OH)₂(CO₃)_(0.165).0.5H₂O used as a rawmaterial in Example 5.

Comparative Example 3

[0055] Zinc-type, carbonate-anion-possessing hydrotalcite particleshaving a BET specific surface area of 8.9 m²/g and represented by achemical formula of Zn_(0.67)Al_(0.33)(OH)₂(CO₃)_(0.165).0.5H₂O werecalcined at 550° C. for 2 hours, to give composite metal oxide solidsolution particles Zn_(0.67)Al_(0.33)O_(1.165) having a BET specificsurface area of 121 m²/g.

Comparative Example 4

[0056] The composite metal oxide solid solution particles obtained inComparative Example 3 and decarboxylated water having a weightapproximately 10 times the weight thereof were placed in a container,and the container was closed and shaken in a constant-temperaturechamber at 30° C. overnight, to carry out a rehydrative reaction. Theresultant mixture was dehydrated and dried to give Zinc-type,hydrotalcite-like composite metal hydroxide particlesZn_(0.67)Al_(0.33)(OH)_(2.22)(CO₃)_(0.06).0.6H₂O having a BET specificsurface area of 35 m²/g. The carbonate ion of the above formula is thatwhich was derived from inclusion of CO₂ in air in the process of thedehydration and drying.

Comparative Example 5

[0057] Particles having a BET specific surface area of 2.2 m²/g and achemical formula ofCa_(4.76)Al₂(OH)_(13.2)(NO₃)_(1.7)(CO₃)_(0.31).4.6H₂O were used.

Comparative Example 6

[0058] Magnesium hydroxide particles having a BET specific surface areaof 6.0 m²/g were calcined at 550° C. for 2 hours, to give magnesiumoxide particles having a BET specific surface area of 89 m²/g.

Comparative Example 7

[0059] Reagent Ca(OH)₂ particles were calcined at 550° C. for 2 hours togive calcium oxide particles having a BET specific surface area of 10m²/g.

Comparative Example 8

[0060] Activated carbon (particulate) supplied by Ishizu PharmaceuticalCo. was pulverized and passed through a 100-mesh screen. The activatedcarbon had a BET specific surface area of 443 m²/g.

Comparative Example 9

[0061] Taiko activated carbon (granular) supplied by Nimura Kagaku KKwas used in its original condition. The activated carbon had a BETspecific surface area of 449 m²/g.

[0062] For evaluating the adsorbents obtained in Examples 1 to 6 andComparative Examples 1 to 9 for capability of adsorption to an aromatichydroxy compound, (I) a bisphenol A adsorption test, (II) a phenoladsorption test and (III) a nonylphenol adsorption test that are shownbelow were carried out.

[0063] (I) Bisphenol A Adsorption Test

[0064] 40 Grams of a solution of 100 ppm or 500 ppm of a bisphenol A(BPA) and 0.4 g of an adsorbent (1 wt % to the bisphenol A solution)were placed in a closure-attached Erlenmeyer flask having a volume of300 ml and shaken at 120 rpm at 40° C. for 1 hour. Then, the adsorbentwas separated by filtering, and a filtrate was measured for absorptionaround 280 nm (at 280 nm when the solvent was ethanol, or at 277 nm whenthe solvent was 10 wt % ethanol +90 wt % deionized water) with anabsorptionmeter, to determine a bisphenol A concentration. As abisphenol A solution, there were prepared a solution of bisphenol A inethanol (organic solvent) and a solution of bisphenol A in 10 wt %ethanol +90 wt % deionized water (aqueous solvent). The following Table1 shows the results. The adsorptivity in the table shows a percentage(%) of BPA adsorbed to an adsorbent to BPA in a solvent. TABLE 1Adsorptivity (%) to BPA Adsorptivity (%) to BPA in organic solvent inaqueous solvent Initial con- Initial con- Initial con- Initial con-centration centration centration centration of BPA of BPA of BPA of BPAAdsorbent 100 ppm 500 ppm 100 ppm 500 ppm Ex. 1 36.8 17.7 100 100 Ex. 2100 87.8 100 73.4 Ex. 3 13.3 5.9 100 100 Ex. 4 91.3 88.7 96.4 80.6 Ex. 55.9 1.7 100 99.1 Ex. 6 78.4 48.1 98.4 67.1 C. Ex. 1 0.7 0 1.3 0 C. Ex. 20 0 0 0 C. Ex. 3 0.2 0 57.2 46.2 C. Ex. 4 0 0 39.1 19.2 C. Ex. 5 0 0 * *C. Ex. 6 8.5 8.0 41.9 67.8 C. Ex. 7 24.0 10.7 * * C. Ex. 8 5.5 5.3 10096.1 C. Ex. 9 0 0 90.9 84.3

[0065] (II) Phenol (PH) Adsorption Test

[0066] A phenol (PH) adsorption test was carried out in the same manneras in the above bisphenol A adsorption test except that the bisphenol Awas replaced with phenol and that the wavelength for measurement for anabsorbance was changed to 273.5 nm for quantitative determination. Table2 shows the results. TABLE 2 Adsorptivity (%) to PH in organic solventInitial Initial concentration of concentration of Adsorbent PH 100 ppmPH 500 ppm Ex. 2 99.4 94.6 C. Ex. 8 25.6 13.5

[0067] (III) Nonylphenol (NP) Adsorption Test

[0068] A nonylphenol (NP) adsorption test was carried out in the samemanner as in the above bisphenol A adsorption test except that thebisphenol A was replaced with nonylphenol and that the wavelength formeasurement for an absorbance was changed to 277.5 nm for quantitativedetermination. Table 3 shows the results. TABLE 3 Adsorptivity (%) to NPin organic solvent Initial Initial concentration of concentration ofAdsorbent NP 20 ppm NP 100 ppm Ex. 1 13.3 8.2 Ex. 2 36.9 28.0 C. Ex. 8 04.3

[0069] (IV) Test of Elution of Bisphenol A from Epoxy Resin

[0070] For studying an effect on adsorption to bisphenol A in a resin, asample was prepared by adding a small amount of bisphenol A to a resinduring its processing, and the following elution test was carried out.

[0071] (1) Preparation of Epoxy Resin Sample Composition Sample {circleover (1)} Sample {circle over (2)} Materials (Blank) (Adsorbent added)(a) Epicote 828 100 phr 100 phr (b) Rikacid MH-700  80 phr  80 phr (c)Dimethylbenzylamine  1 phr  1 phr (d) Bisphenol A  0.2 phr  0.2 phr (e)Adsorbent —  1 phr

[0072] Preparation of Samples

[0073] The above composition was stirred at room temperature for 30minutes and dropped in the form of dots having a diameter of 5 mm each,and the dropped composition was pre-cured (110° C.×2 hours) andpost-cured (150° C.×3 hours). 1 Gram of the thus-obtained epoxy resinchips were used as a sample for the elution test.

[0074] (2) Elution Test of Bisphenol A

[0075] 1 Gram of the epoxy resin chips and 10 g of ethanol were placedin a closure-attached Erlenmeyer flask having a volume of 100 ml and theflask was immersed in a constant-temperature vessel set at 40° C. for 5days. After the 5 days, the flask was lightly shaken, and a supernatantwas measured for the bisphenol A with an absorptionmeter. The followingTable shows the results. Concentration (ppm) of BPA in supernatantSample {circle over (1)} 877.0 Sample {circle over (2)} 332.1

[0076] Effect of the Invention

[0077] According to the present invention, there can be provided anadsorbent that can efficiently remove an aromatic hydroxy compound byadsorption from an aqueous or organic solvent containing an aromatichydroxy compound. Above all, an aromatic hydroxy compound can beeffectively removed from an organic solvent completely free of water.

1. An adsorbent to an aromatic hydroxy compound, which comprisescomposite metal oxide solid solution particles of the following formula(1) or hydrotalcite-like composite metal hydroxide particles of thefollowing formula (2), (Mg_(y1)M²⁺ _(y2))_(1−x)Al_(x)O_(1+0.5x)  (1)(Mg_(y1)M²⁺ _(y2))_(1−z)Al_(z)(OH)_(2+a)(A^(n−))_(b) .mH₂O  (2) whereinM²⁺ is divalent metal ion or ions of Zn²⁺ and/or Ca²⁺, A^(n−) is ananion having a valence of n, and y₁, y₂, x, z, a, b and m satisfy thefollowing conditions, y ₁ +y ₂=1 0<y ₁≦1 0.1<x<0.5 0.1<z<0.5 z=a+nba>0.1z 0≦b<z/n 0≦m<2.
 2. The adsorbent of claim 1, wherein the A^(n−)inthe formula (2) is at least one anion selected from the group consistingof CO₃ ²⁻, SO₄ ²⁻, Cl⁻, NO₃ ⁻ and CH₃COO⁻.
 3. The adsorbent of claim 1,wherein the particles have the form of particles, powders, granules orpellets.
 4. The adsorbent of claim 1, which is composed of particleshaving a BET specific surface area of 10 to 250 m²/g.
 5. The adsorbentof claim 1, wherein the content of the composite metal oxide solidsolution particles of the formula (1) and/or the hydrotalcite-likecomposite metal hydroxide particles of the formula (2) is at least 50%by weight.
 6. The adsorbent of claim 1, wherein the aromatic hydroxycompound is at least one member selected from the group consisting ofphenol, alkyl-substituted phenol, nitrophenol and bisphenol A.
 7. Theadsorbent of claim 1, wherein y₁, y₂, x and z in said formulae (1) and(2) satisfy the following conditions, y ₁ +y ₂=1 0.5<y ₁≦1 0.2≦x≦0.40.2≦z≦0.4.
 8. The adsorbent of claim 1, wherein a, b, n and m in theformula (2) satisfy the following conditions, z=a+nb a>0.5z 0≦b<0.5z/n0≦m≦1.
 9. A column charged with the composite metal hydroxide solidsolution particles of the formula (1) in claim 1, for removing anaromatic hydroxy compound by adsorption.
 10. A column charged with thehydrotalcite-like composite metal hydroxide particles of the formula (2)in claim 1, for removing an aromatic hydroxy compound by adsorption. 11.A method of removing an aromatic hydroxy compound in an aqueous solventor organic solvent containing an aromatic hydroxy compound, whichcomprises bringing the said solvent containing the aromatic hydroxycompound and the adsorbent of claim 1 into contact with each other toallow the adsorbent to adsorb the aromatic hydroxy compound.
 12. Themethod for removing an aromatic hydroxy compound of claim 9, wherein theaqueous solvent is a solvent containing at least 60% by weight of water.13. A method of removing an aromatic hydroxy compound in an aqueoussolvent containing an aromatic hydroxy compound, which comprisesbringing the said solvent containing the aromatic hydroxy compound andthe adsorbent of claim 1 into contact with each other to allow theadsorbent to adsorb the aromatic hydroxy compound.
 14. A method ofremoving an aromatic hydroxy compound in an organic solvent containingan aromatic hydroxy compound, which comprises bringing the said solventcontaining the aromatic hydroxy compound and an adsorbent composed ofthe hydrotalcite-like composite metal hydroxide particles of the formula(2) in claim 1 into contact with each other to allow the adsorbent toadsorb the aromatic hydroxy compound.
 15. The method for removing anaromatic hydroxy compound of claim 11, 13 or 14, wherein the organicsolvent is a solvent containing at least 60% by weight of at least oneorganic solvent selected from the group consisting of a lower alcohol,an ether, a ketone and an aromatic hydrocarbon.
 16. A resin compositionor coating composition comprising a synthetic resin or paint synthesizedfrom an aromatic hydroxy compound as a raw material and the adsorbent ofclaim
 1. 17. The resin composition or coating composition of claim 16,which contains, per 100 parts by weight of the synthetic resin or paint,0.01 to 10 parts by weight of the adsorbent.
 18. The resin compositionor paint composition of claim 16, wherein the adsorbent is an adsorbentcomposed of the hydrotalcite-like composite metal hydroxide particles ofthe formula (2) in claim
 1. 19. The resin composition of claim 16,wherein the synthetic resin is a polycarbonate resin or epoxy resinsynthesized from bisphenol A as a raw material.